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Next: <a href="C-Extensions.html#C-Extensions" accesskey="n" rel="next">C Extensions</a>, Previous: <a href="C-Implementation.html#C-Implementation" accesskey="p" rel="prev">C Implementation</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Indices.html#Indices" title="Index" rel="index">Index</a>]</p>
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<a name="C_002b_002b-Implementation_002dDefined-Behavior"></a>
<h2 class="chapter">5 C++ Implementation-Defined Behavior</h2>
<a name="index-implementation_002ddefined-behavior_002c-C_002b_002b-language"></a>

<p>A conforming implementation of ISO C++ is required to document its
choice of behavior in each of the areas that are designated
&ldquo;implementation defined&rdquo;.  The following lists all such areas,
along with the section numbers from the ISO/IEC 14882:1998 and ISO/IEC
14882:2003 standards.  Some areas are only implementation-defined in
one version of the standard.
</p>
<p>Some choices depend on the externally determined ABI for the platform
(including standard character encodings) which GCC follows; these are
listed as &ldquo;determined by ABI&rdquo; below.  See <a href="Compatibility.html#Compatibility">Binary
Compatibility</a>, and <a href="https://gcc.gnu.org/readings.html">https://gcc.gnu.org/readings.html</a>.  Some
choices are documented in the preprocessor manual.
See <a href="../cpp/Implementation_002ddefined-behavior.html#Implementation_002ddefined-behavior">Implementation-defined
behavior</a> in <cite>The C Preprocessor</cite>.  Some choices are documented in
the corresponding document for the C language.  See <a href="C-Implementation.html#C-Implementation">C Implementation</a>.  Some choices are made by the library and operating
system (or other environment when compiling for a freestanding
environment); refer to their documentation for details.
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<tr><td align="left" valign="top">&bull; <a href="Conditionally_002dsupported-behavior.html#Conditionally_002dsupported-behavior" accesskey="1">Conditionally-supported behavior</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
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<tr><td align="left" valign="top">&bull; <a href="Exception-handling.html#Exception-handling" accesskey="2">Exception handling</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
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